The invention relates to an electrical lamp provided with a cap comprising:
a gas-filled translucent lamp vessel scaled in a vacuum-tight manner and having a pinch seal; PA0 an electrical element arranged within the lamp vessel; PA0 current conductors passing through the wall of the lamp vessel to the electrical element; PA0 a metal clamping plate having an opening in which the pinch seal is held fast by lugs formed in the clamping plate, which clamping plate has a substantially circular-cylindrically flanged edge or collar; PA0 a substantially circular-cylindrical metal sleeve having first and second ends which is joined telescopically at its first end to the collar of the clamping plate and is rigidly secured thereto; PA0 the lamp cap comprises a first substantially circular-cylindrical hollow body of synthetic material which is provided with a circumferential ridge and a second body of synthetic material rigidly connected to each other. The second body has a disk-shaped portion having an upright edge and a projecting flange, the upright edge of the second body surrounding the first body at a first end thereof and having an end surface. The end surface and the circumferential ridge form opposed walls of a circumferential groove for a sealing ring, and in that PA0 the first, substantially cylindrical, body and the metal sleeve have cooperating means which lock the sleeve against displacement.
a cup-shaped lamp cap of synthetic material in which the second end of the metal sleeve is fixed and which has a bottom portion and a substantially cylindrical wall portion and is provided at its outer surface with a projecting flange and, at the side thereof facing the lamp vessel, with a circumferential groove for receiving a sealing ring, electrical contacts connected to the current conductors being secured to the bottom portion.
Such an electrical lamp is known from U.S. Pat. No. 4,412,273 (Patent Treuhand Gesellschaft fur Elektrische Gluhlampen mbH).
The known lamp is suitable to be used as a headlight for vehicles, the lamp vessel projecting through the opening of a reflector provided with a front glass. The projecting flange of the lamp cap of synthetic material then abuts against the edge of the opening in the reflector. A ring of, for example, silicon rubber received in the circumferential groove in the outer surface of the lamp cap then seals the interior of the lantern constituted by the reflector and the front glass from the environment.
A disadvantage of the known lamp is that the lamp cap of synthetic material is of a rather complicated form, as a result of which multipartite molds are required to form the body. Another disadvantage is that it is difficult to fix the metal sleeve in the lamp cap. The aforementioned U.S. Patent is silent as to the manner in which the metal sleeve is fixed in the lamp cap. Nevertheless the usability of the lamp depends completely upon whether a rigid connection of the sleeve to the lamp cap is or is not available. In fact, the light-emitting electrical element or elements of the lamp should be located at a predetermined area when mounting the lamp in a reflector. For this purpose, the element(s) should occupy a predetermined position with respect to reference points on the flange of the lamp cap and should also retain this position over a prolonged period of use of the lamp. When the pinch seal is rigidly secured in the clamping plate and when the clamping plate is rigidly secured to the metal sleeve, the electrical element being aligned with respect to the flange of the lamp cap, the connection of this sleeve to the lamp cap is determinative of the quality of the lamp.